山区天气不定,救援队必须随时调整行进路线。Shānqū tiānqì búdìng, jiùyuán duì bìxū suíshí tiáozhěng xíngjìn lùxiàn.Mountain weather is unstable, so the rescue team must adjust its route at any time.
他的上班时间不定,有时早,有时很晚。Tā de shàngbān shíjiān búdìng, yǒushí zǎo, yǒushí hěn wǎn.His working hours are irregular, sometimes early and sometimes very late.
这个周末去不去爬山还不定,要看天气。Zhège zhōumò qù bú qù páshān hái búdìng, yào kàn tiānqì.It is still undecided whether we will go hiking this weekend; it depends on the weather.